A semiconductor wafer can be separated into individual dies and packaged as microchips (integrated circuits). These microchips can be quality tested to assure satisfactory performance. Microchips that fail quality testing reduce yields and increase effective per microchip fabrication costs. Failure analysis may be performed in an effort to improve the fabrication process and increase yields, and testing during the fabrication process may facilitate failure analysis. However, testing time during fabrication also reduces overall yields.
One parameter that can be tested for in a semiconductor structure is Bias Temperature Instability (BTI). BTI can occur when the device is subjected to elevated temperatures and high gate voltages while the remaining terminals are grounded. Device characteristics can be negatively impacted when a device is subject to high voltage and thermal stress. For example, a threshold voltage can change with high voltage and increased thermal stress.
BTI characterization is costly to develop in view of time requirements for performance of testing. A microchip can include a limited number of macro contact pads that are of such size to be contacted by probes of an external test unit. In one form, an external unit can include a source measurement unit (SMU).